This invention relates to solar energy collecting apparatus. More particularly it is concerned with elongated evacuated tube solar energy collectors.
Among the developments in the art of solar energy apparatus are evacuated tube collectors which employ an evacuated glass tube surrounding an energy absorber. Vacuum insulation prevents conduction and convection losses from the energy absorber thus allowing higher operating temperatures and improving efficiency. Recent developments in elongated solar energy reflecting and concentrating structures, specifically structures of compound parabolic configuration, have contributed to improvements in non-tracking collectors of high efficiency. An improved non-tracking elongated evacuated tube solar energy collector employing compound parabolic reflectors and a straight-through fluid flow heat transfer construction is described and claimed in copending application Ser. No. 334,605 filed Dec. 28, 1981 by Sandford C. Peek and assigned to the assignee of the present application.
In solar energy collecting apparatus of the general type as described the energy absorber should be located at its proper position at the focus of the reflected insolation in order to obtain high efficiency. To provide proper positioning of the energy absorber throughout the rather long span in an elongated evacuated collector at the operating temperature produced, the energy absorber must be supported at intermediate points along its length in addition to being supported at the ends of the evacuated tube. Energy absorber supporting devices heretofore available were complicated, employed several parts, required structure for attachment to the tube, blocked insolation impinging on the energy absorber, and/or provided a significant path for thermal losses from the energy absorber.